<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <style>
        body{
            background: black;
        }
        .moon{
            width: 200px;
            height: 200px;
            border-radius: 50%;
            box-shadow: 40px 40px 0 0 #ffffff;
        }
    </style>
</head>
<body>
    <div class="moon"></div>
</body>
</html>